<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>加法计算器</title>
</head>
<body>
<form>
    第一个数字<input type="text" id="firstNum" value=" "><br>
    第二个数字<input type="text" id="lastNum"><br>
    <button id="calc" onclick="calc()">计算</button>
</form>
<script src="js/common.js"></script>
<script>
    let a = $("firstNum").value;
    let b = $("lastNum").value;
    let res;
    function calc() {
        alert(a);
    };
</script>
</body>
</html>